Threadfin Butterflyfish

The Threadfin Butterflyfish is a big, gorgeous butterflyfish that’s often available and hardy!

The Threadfin Butterflyfish Chaetodon auriga is a real attraction. It has a bold elegant appearance and a bold personality to match. It is one good sized butterflyfish, reaching a length of just over 9 inches (23 cm). In nature it has a calm approachable demeanor and readily allows divers to observe and photograph it. In the aquarium it is equally forthcoming once it’s adapted, and it makes a spectacular show piece.

The coloration and patterning of this butterfly fish just can’t be beat. The body is a bright pearly white to the front and becomes bright yellow to the rear and onto the dorsal, anal and tail fins. It sports a number of diagonal black lines that are perpendicular to one another, creating a chevron-type patterning. It’s accented with a bold black eye bar running vertically across its face and it may or may not have a black eye spot high up on the back half of the dorsal fin.

Yet one of its most fantastic features, seen on full grown adults, is a long pennant type extension streaming from the fifth and sixth filaments of the dorsal fin. Thus its common name Threadfin Butterfly was derived. It is also known by the popular term Auriga Butterflyfish, which identifies it by is scientific name. Several other descriptive names it is known by include Cross-stripe Butterfly, Whip Butterflyfish, Threadfin Coralfish, Diagonal Butterflyfish, and Yellow butterflyfish.

A couple very close relatives of this fish are the Vagabond ButterflyfishChaetodon vagabundus and the Indian Vagabond Butterflyfish Chaetodon decussatus. These three fish are similar in appearance with the characteristic chevron type patterning, but have noticeable differences in the color patterning to the rear portions of their body.

This prominent butterflyfish is quite hardy. It readily adapts to aquarium life and will feed on all sorts of aquarium foods, making it a great fish for the beginner. It is a large fish however, and when it attains its full adult size it will need a larger than average, well established aquarium. A 100 gallon tank is the minimum suggested size. Decorate the tank with rocks creating many caves for hiding places along with plenty of swimming space. It swims freely and usually spends a good deal of its time in the open water, moving in and out of crevices as it forages for food.

These are one of the best all around butterflyfish and does quite well in a fish only community environment. They get along with most other marine fishes, basically just ignoring them. Yet they are one of the more aggressive butterflyfish and will often chase conspecifics and others with a similar color pattern and shape. For the best success in keeping more than one butterfly, provide a very large tank and introduce them at the same time. Many reef-keepers hope to keep it in a mini reef, but as it is a coral eater and will snack on all types of other reef inhabitants, it is best kept in a fish only community tank.

For more Information on keeping saltwater fish see:
Marine Aquarium Basics: Guide to a Healthy Saltwater Aquarium

Habitat: Distribution / Background

The Threadfin Butterflyfish Chaetodon auriga was described by Forsskal in 1775. They have a very wide distribution and are found in the entire Indo-Pacific region. It is one of the more common butterflyfishes of the Australia-New Guinea region. They are found in the Red Sea, in the Indo-Pacific from eastern coast of Africa and eastward to Hawaii, the Marquesas Islands (French Polynesia), and Ducie Atoll (Pitcairn Islands, UK), north to southern Japan and south to Australia including the Lord Howe and Rapa islands, as well as in the Eastern Pacific from the Galapagos Islands of Ecuador.

The coloring and body shape of these fish can be quite variable across its range and a number of “accidental hybrids have also been reported. Specimens from the Red Sea differ from all the rest in that they have no eye spot (ocellus) on their dorsal fin. Allen (1979) suggested this group of fish consists of two subspecies, with the Red Sea variety being Chaetodon auriga auriga and all the rest being Chaetodon auriga setifer.

This species is one of a closely related group of butterflyfishes that belong to the subgenus Rabdophorus, which may eventually become a distinct genus. This is a large group that are being identified as related through modern DNA sequence data. Some very close relatives of this fish that are similar in appearance are the Vagabond Butterflyfish Chaetodon vagabundus and the Indian Vagabond Butterflyfish Chaetodon decussatus. These three share the characteristic chevron type patterning, but have noticeable differences in their hindpart coloration. Other members of the Rabdophorus subgenus that these fish are known to crossbreed with are the Raccoon ButterflyfishChaetodon lunula and the Saddled ButterflyfishChaetodon ephippium.

This species is on the IUCN Red List as Least Concern (LC). They have a wide distribution and are typically abundant. There have been some localized population declines and they are harvested for the aquarium trade, but thereare no major threats identified overall. Other common names they are known by include Auriga Butterflyfish, Cross-stripe Butterfly, Whip Butterflyfish, Diagonal Butterflyfish, Threadfin Coralfish, Yellow butterflyfish, and Threadfin Butterfly.

These butterflyfish inhabit a variety of environments at both inner and outer reefs, and in lagoons. They tend to prefer coral rich areas on reef flats and on fore-reef slopes, but are also found in coral sparse areas that are strewn with rubble and weeds. They inhabit depths from 3 – 200 feet (1 – 61 meters), but are usually found at depths less than 98 feet (30 m). Adults are mostly found in pairs or sometimes alone. Occasionally they are seen in groups of about 3 to 10 individuals or grouped with the Double Saddle Butterflyfish Chaetodon ulietensis. Juveniles are usually found singly and in shallower waters that the adults.

Their diet is very vast, though it varies somewhat depending on where they live. They will tear off pieces of invertebrate prey and graze on filamentous algae. Foods varieties range from algae, soft corals, hard corals, anemones, polychaetes, gastropods (snails) to hydroids, peanut worms, nematode worms, mollusk eggs, amphids, shrimps, sea cucumber tentacles, the feet of sea urchins, tunicates and other small crustaceans. They spend most of their time foraging for food items among coral rubble and crevices in the reef. They will also forage on the sand, and are often associating with goatfishes that disturb the substrate exposing worms that are a delectable delight for these fish.

• Scientific Name: Chaetodon auriga
• Social Grouping: Pairs – They are usually seen in pairs, though sometimes in small groups of 3 to 10 individuals or singly. Juveniles are solitary.
• IUCN Red List: LC – Least Concern

Description

The Threadfin Butterflyfish has the typical butterflyfish shape. Its body is oval, though it is one of the more elongated species, and it is laterally compressed. It has a protruding snout tipped with a small mouth and a rounded tail fin. The dorsal fin is continuous and has a long pennant type extension streaming from the fifth and sixth filaments on mature adults. This species can reach just over 9 inches (23 cm) in the wild, but are generally a bit smaller in the aquarium. It typically has a lifespan of about 5 years, but could live longer with proper care.

The adult C. auriga is a bright white to the front and becomes bright yellow to the rear and onto the dorsal, anal and tail fins. It has a number of diagonal black lines that are perpendicular to one another, creating a chevron-type patterning. There is a bold black eye bar running vertically across its face. It may or may not have a black eye spot high up on the later half of the dorsal fin. This spot is missing on adults originating from the Red Sea.

• Size of fish – inches: 9.1 inches (23.01 cm) – They are usually a bit smaller in the aquarium.
• Lifespan: 5 years – The average lifespan is about 5 years, but it could live longer with proper care.

Fish Keeping Difficulty

This is a hardy butterflyfish and is one of the best of its family for the beginning aquarist. They will generally acclimate quickly and readily eat all sorts of aquarium foods. They do need a larger aquarium than others of their family, but are disease resistant and will prove to be a sturdy aquarium fish.

• Aquarium Hardiness: Moderately hardy
• Aquarist Experience Level: Beginner

Foods and Feeding

The Threadfin Butterflyfish are omnivores, in the wild they feed on algae, stony coral polyps, soft corals, anemones, and all sorts of non-coralline invertebrates. In the aquarium it is important that you feed a good variety of live, frozen, and prepared formula foods with emphasis on vegetables and spirulina. These foods can include live brine, flakes, and frozen foods of all kinds including Formula I, Formula II, Angel Formula and spirulina. Japanese Nori will also be favored. Several sponge based frozen foods are now available and can also be fed to butterflyfish. Feed it at least twice a day, and if it is a tiny juvenile feed it three to four times everyday.

• Diet Type: Omnivore
• Flake Food: Yes
• Tablet / Pellet: Yes
• Live foods (fishes, shrimps, worms): Some of Diet
• Vegetable Food: Some of Diet
• Meaty Food: Some of Diet
• Feeding Frequency: Several feedings per day – Offer various foods quite frequently at first. Once acclimated adults need at least 2 feedings a day and juveniles need 3 to 4.

Aquarium Care

Once adapted no special care or technique is needed to maintain this fish in the aquarium. Frequent water changes are not necessary, rather normal water changes at 10% biweekly or 20% monthly are fine. Sudden massive water changes can cause trouble.

• Water Changes: Bi-weekly – Change 10% biweekly or 20% monthly, avoid sudden massive water changes.

Aquarium Setup

These fish need plenty of space to accommodate their size and to swim. As they can reach a whooping 9 inches in length, a 100 gallon tank is the minimum suggested size. The tank should be well decorated with lots of rocks creating numerous places for retreat and lots of rubble. They also need plenty of open space for swimming. This fish is a coral eater, nipping the polyps of hard stony coral species. It will also tear apart most other invertebrates it finds. Consequently it is not recommended for coral-rich reefs.

• Minimum Tank Size: 100 gal (379 L)
• Suitable for Nano Tank: No
• Live Rock Requirement: Typical Plus Hiding Places
• Substrate Type: Mix – Sand + Coral
• Lighting Needs: Moderate – normal lighting – It is best kept under the normal lighting conditions, but can also be kept under very bright light as long as some dimly lit spaces are provided.
• Temperature: 72.0 to 82.0° F (22.2 to 27.8&deg C)
• Specific gravity: 1.020-1.025 SG
• Range ph: 8.1-8.4
• Brackish: No
• Water Movement: Weak – Water movement is not a significant factor. It can tolerate a rather strong flow but slow-moving water is recommended.
• Water Region: All – It swims freely and usually spends time in the open water.

Social Behaviors

The Threadfin Butterflyfish is best kept in a large fish only community tank. This fish is non-aggressive to other fish, and will basically ignore its other non-related tankmates. Yet they are one of the more aggressive butterflyfish and will often chase conspecifics and others with a similar color pattern and shape. For the best success in keeping more than one butterfly, provide a very large tank and introduce them at the same time. They are not suited for the reef aquarium as they will feed on coral polyps, anemones, and a wide range of other invertebrates and crustaceans,

Smaller non-aggressive fishes like cardinalfish, gobies, tilefish, fairy basslets, fairy and flasher wrasses are good candidates as tank mates. Larger and rather territorial angelfish like Pomacanthus and Holacanthus can be kept together with this species. Also other angelfish like members of Centropyge, Apolemichthys, Genicanthus, Chaetodontoplus and Pygoplites also can be good tank mates.

• Venomous: No
• Temperament: Peaceful – It generally ignores most other tankmates.
• Compatible with:
  • Same species – conspecifics: Sometimes – To keep with other butterflyfish the tank needs to be very large and they should be introduced at the same time.
  • Peaceful fish (gobies, dartfish, assessors, fairy wrasses): Safe
  • Semi-Aggressive (anthias, clownfish, dwarf angels): Safe
  • Monitor
  • Large Semi-Aggressive (tangs, large angels, large wrasses): Monitor
  • Large Aggressive, Predatory (lionfish, groupers, soapfish): Threat
  • Monitor
  • Anemones: Threat
  • Mushroom Anemones – Corallimorphs: Threat
  • LPS corals: Threat
  • SPS corals: Threat
  • Gorgonians, Sea Fans: Threat
  • Leather Corals: Threat
  • Soft Corals (xenias, tree corals): Threat
  • Star Polyps, Organ Pipe Coral: Threat
  • Zoanthids – Button Polyps, Sea Mats: Threat
  • Sponges, Tunicates: Threat
  • Shrimps, Crabs, Snails: Threat
  • Starfish: Threat
  • Feather Dusters, Bristle Worms, Flatworms: Threat
  • Clams, Scallops, Oysters: Threat
  • Copepods, Amphipods, Mini Brittle Stars: Threat

Sex: Sexual differences

No sexual difference is noted for this species. Butterflyfish species studied up to this time indicate that these fish are gonochoristic, meaning that each fish is either a male or a female and they do not change sex.

Breeding / Reproduction

This species has not been cultivated in captivity. In the wild butterflyfish are pelagic spawners that release many tiny eggs into the planktonic water column where they float with the currents until they hatch. Once hatched the fry are in a post-larval where their body, extending from the head, is covered with large bony plates.

Marine butterflyfish have not reportedly been spawned successfully in captivity. There are however, reports of some success in rearing wild collected larvae of some of the corallivorous butterflyfish. It is hoped these captive reared fish will be adapted to accept aquarium foods, and thus broaden the species selections that can be sustained in captivity. For more information see, Marine Fish Breeding: Butterflyfish.

• Ease of Breeding: Unknown

Fish Diseases

The Threadfin Butterflyfish are generally hardy and problems with disease are minimal in a well maintained aquarium. Any additions to a tank can introduce disease, so it’s advisable to properly clean or quarantine anything that you want add to an established tank prior to introduction.

Diseases that marine Butterflyfish are susceptible to include Marine Ich(white spot disease), Marine Velvet, Uronema marinum, and Lymphocystis. Some can be treated successfully with medical care or copper drugs, but some species hate sudden changes of water including pH, temperature, or any drug treatment. In the wild a cleaner wrasse (Labroides sp.) will help them by taking parasites from their bodies, however these wrasses are extremely difficult to sustain in captivity. Alternative fish such as Neon Gobies (Gobiosoma spp.) can help them by providing this cleaning service in the home aquarium.

This butterflyfish is a stony coral eater and it can also be sensitive to some drugs. Be sure to observe this fish closely when medicating it, so you can remove it if it shows signs of stress. For information about saltwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.

Availability

The Threadfin Butterflyfish is one of the more popular butterlyfish. They are generally available in pet stores and online, and are relatively moderate in price.

References

• Animal-World References: Marine and Reef
• Chaetodon auriga (ForsskÃ¥l, 1775) Threadfin butterflyfish, Fishbase.org
• Chaetodon auriga, The IUCN Red List of Threatened Species
• Helmut Debelius, Rudie H. Kuiter, World Atlas of Marine Fishes, Hollywood Import & Export. Inc., 2006
• Scott W. Michael, The 101 Best Saltwater Fishes: How to Choose & Keep Hardy, Brilliant, Fascinating Species That Will Thrive in Your Home , TFH Publications, 2007
• Scott W. Michael, Angelfishes & Butterflyfishes: Reef Fishes Series , Microcosm Ltd, 2004
• Butterflyfish Compatibility With Corals, Orphek.com, Copyright 2009 – 2012
• Robert M. Fenner, The Conscientious Marine Aquarist: A Commonsense Handbook for Successful Saltwater Hobbyists , TFH Publications, 2001
• Mark Allen, Roger Steene and Gerald R. Allen, A Guide to Angelfishes and Butterflyfishes , Odyssey Publishing, 1998
• Dr. Warren E. Burgess, Dr. Herbert R. Axelrod, Raymond E. Hunziker III, Dr. Burgess’s Atlas of Marine Aquarium Fishes, T.F.H Publications inc., 1990
• Roger Steene, Gerald R. Allen, Hans A. Baensch, Butterfly and Angelfishes of the World, Volume 1, John Wiley & Sons, 1980

Fähnchen-Falterfisch (Chaetodon auriga) (Image Credit: Holger Krisp, Wikimedia Commons CC BY-SA 3.0 Unported)